These are among the standard warnings for lots of sleeping pills. And that’s fine if you don’t have to go out on the highway or operate a backhoe.

But what if your workplace 24 hours per day is a big, heavy, hazardous machine in outer space, like the shuttle of the International Space Station?

US astronauts Reid Wiseman (left) and Steve Swanson (right) join German astronaut Alexander Gerst for some gravity-free football aboard the International Space Station. The majority of astronauts rely on sleeping tablets to rest and get far less than the recommended 8 hours. Photo: AFP

The question is getting renewed attention in the most extensive study to date of the sleeping habits of astronauts as recorded in flight. They’ve got a problem sleeping, it said, and lots of them, up to three-fourths, take medication to help them doze off.

Advertisement

The study, by researchers at Brigham and Women’s Hospital (BWH), Harvard Medical School and the University of Colorado, is published in the Lancet Neurology and summarised in a release from Brigham and Women’s.

It looked at the data from more than 4200 nights spent in space by 64 astronauts on 80 shuttle missions and 21 astronauts aboard International Space Station (ISS) missions.

“Crew members attempted and obtained significantly less sleep per night” than would otherwise be the case, the study found. Though NASA recommends eight hours of sleep for astronauts, the study said as a group they averaged just less than six hours on shuttle missions and just more than six hours on the space station. They also got less sleep just before flights as well, it said.

To help themselves sleep, the researchers found “widespread use of sleeping medications such as zolpidem and zaleplon during space flight,” said the summary. “Three-quarters of ISS crew members reported taking sleep medication at some point during their time on the space station, and more than three-quarters (78 per cent) of shuttle-mission crew members used medication on more than half (52 per cent) of nights in space.”

“Sleep deficiency is pervasive among crew members,” Laura Barger of BWH’s Division of Sleep and Circadian Disorders, stated in the BWH press release. “It’s clear that more effective measures are needed to promote adequate sleep in crew members, both during training and space flight, as sleep deficiency has been associated with performance decrements in numerous laboratory and field-based studies.”

“The ability for a crew member to optimally perform if awakened from sleep by an emergency alarm may be jeopardised by the use of sleep-promoting pharmaceuticals,” said Barger. “Routine use of such medications by crew members operating spacecraft are of particular concern, given the US Federal Drug Administration warning that patients using sleeping pills should be cautioned against engaging in hazardous occupations requiring complete mental alertness or motor coordination, including potential impairment of performance of such activities that may occur the day following ingestion of sedative/hypnotics. This consideration is especially important because all crew members on a given mission may be under the influence of a sleep promoting medication at the same time.”

This problem is not news to NASA, though the extent of sleeplessness and of medication use is greater than earlier studies reported. In 2001, an agency press release, “Wide Awake in Outer Space,” highlighted the issue:

Astronauts sleep poorly in space and it’s no wonder. Just consider: the excitement of blasting off on a powerful rocket, the strange sensations of floating in free-fall, the novelty of mornings that return every 90 minutes. Who could sleep through all that?

The study was supported by NASA and the National Space Biomedical Research Institute.